LENTON Taper Treaded Rebar Splicing Systems

For many years now, the splicing of reinforcing bars at a construction site was absent, as the predominant method of construction was the erection of buildings of reinforced concrete slabs. But in the last decade, due to the active construction of buildings and structures of reinforced concrete construction and the transition to the use of thermo-mechanically reinforced rebar A500C class DSTU 3760, the problem has become urgent.

Existing regulations in Ukraine for design of reinforced concrete structures, including those for seismic regions, for splicing reinforcement concrete structures allow for a method of welding and lap connection without welding. But as practice shows, such compounds have a number of drawbacks.

Welded connection necessitates more expensive and complicated the progress of work at the expense of labor. To create these connections need to attract highly qualified welders. In addition, there are difficulties in controlling the quality of weld seams. Taken together, these elements lead to a substantial increase in labor costs and the cost of manufacture of metal skeletons of concrete structures.

Easier and more common connection is lap joint of rebar without welding. But a serious drawback to this method is overrun by-pass rebar. In addition, in the area of ​​overlap there is a need of additional transverse reinforcement, which leads to difficulty in the area of ​​concrete work more saturated armature designs. It should be noted that when connecting the rebar overlap transfer efforts from one bar to another across the surrounding joint concrete. The destruction of the protective layer of concrete in the area of ​​overlap can eventually lead to complete destruction of the structure.

The world practice has considerable experience in periodic profile rebar splicing with connectors - couplers. The most promising rebar splicing system with a coupler on the tapered thread. This technology is used in the building of the tower of "Mercury" (Fig. 2 a-г), and the tower "Federation" (Fig. 2 д) of the business center "Moscow City", fourth ring road junction in Moscow, Novovoronezh, dry storage nuclear waste in Krasnoyarsk, cable-stayed bridges "Eastern Bosphorus" (Fig. 2 e-ж), and the "Golden Horn" in Vladivostok (Russia), the tower "Burj Khalif" (UAE) (Fig. 2 з), a high-rise complex "Petronas" (Malaysia) (Fig. 2 к), a multifunctional high-rise complex «Z-towers» (Fig. 2, л) and the Latvian National Library in Riga (Latvia), the stadium "Allianz Arena" in Munich (Germany) "Olympic Stadium" in Athens (Greece), the NPP "Olkiluoto» (Finland).

Beginning in 2008, is promoted in Ukraine rebar splicing technology with taper threaded couplers Lenton produced by the American company Erico. The system has an internal tapered thread coupler Lenton, and the connecting bars - tapered thread ends. This connection provides a fast connection and a lack of self-centering of damage during splicing thread. When applied uniformly tapered thread cut off all the layers of reinforced thermo valve, which ensures even distribution of stresses in the application thread on the fitting.

Fig. № 1 Diagram of a mechanical connection with conical thread

The figure № 1 shows the job of mechanical connection tensile force is distributed evenly across all of the threads that are in the coupler and engage the threads come on heat-treated and hardened areas of reinforcement.

In State Companies NIISK conducted a series of tests of mechanical connections reinforcement class A400C and A500C taper threaded couplers Lenton. The test is the connection with the standard coupler A12 (designed for connecting bars of the same diameter as one of the abutting rod is free to rotate, and it is moved in the axial direction is not limited (Fig. 3 a, б)) and positional P13 coupler (designed to connection bars of the same diameter, where none of the abutting bars can not move freely, while moving in the axial direction the bar attached is limited (Fig. 3 в, г).)

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Fig. 2. Examples of the use of technology of couplers splicing rebar with tapered threads Lenton

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Fig. 3. Couplers Lenton

Under the direction of Doctor of Technical Sciences Klimov, taking into account suggestions and comments of scientists SC NIISK, DerzhdorNDI was developed and received a positive conclusion of state examination and conclusion NTS Ministry of Regional Development and Construction of Ukraine the draft national standard of Ukraine. As a result of this work, the construction industry of Ukraine received national standard DSTU-NB-155 B.2.6: 2010 "Guidelines for the application couplers connections with tapered threads in the design and manufacture of reinforced concrete structures." This standard was adopted and promulgated by the Ministry of Regional Development and Construction of Ukraine of December 28, 2010 № 563.

Nowadays it is a couplers mechanical connection with tapered threads Lenton has wide application and on our construction market. Thus, the mechanical connection Lenton used in performing a number of structures (the compound of the rebars and steel-concrete columns, connection for reinforced concrete beams with steel structure stiffness composite columns for reinforcing slabs, etc.) construction of the tallest building in Ukraine - Business center ˝Sky tower˝ in Kiev.

Advantage couplers connection Lenton felt builders of the Crimea. Hotel complex "Crimean Riviera Radisson» in Alushta (Fig. 4), where all vertical reinforcement designs executed by technology Lenton, which can significantly reduce execution time work on the production of monolithic reinforced concrete frame building in contrast to connection for these structures by welding on a metal bracket, lining (type C15-Pc in accordance GOST 14098). To check this fact was intended economic effect on the example of the construction of the real objects of the introduction of mechanical connection rebars with tapered thread couplers Lenton. The calculation was made by comparing the cost of connections Lenton couplers; weld type C12-Pc according to GOST 14098 and lap joints without welding.

Fig. 4. Hotel complex "Crimean Riviera Radisson» in Alushta

Table 1 Number of mounted of rebars couplers connections Lenton for one shift

Rebar diameter, mm

Number of connections (threading and installation), pc

12

492

14

480

16

462

18

431

20

308

22

295

25

277

28

246

32

185

36

154

40

123

The cost of the valve was taken as the average of the results of the analysis of price lists 11 providers as of 04.2011 years

Calculation results are presented in Figure 5.

As can be seen from Fig. 5, a significant economic effect of the introduction of tapered thread mechanical connections of rebars with couplers Lenton (from 9.5%) compared to the lap joints without welding possible to obtain at jointing rebars with nominal diameter of 28 mm to 40 mm. mm.

In this case, would like to point out the fact the cost of coupler connection Lenton below the cost of welded joints for all nominal diameters of the rebars. This fact can be explained by a significant complexity and high cost performance of welded joints.

In addition to matching of the connection Lenton the properties requirements of domestic and foreign standards, the introduction of technology Lenton can connection for a significant economic effect when connecting rebar nominal diameter of 28 mm to 40 mm. This significantly reduces construction time, no need to connect the rebar to attract highly skilled workers.

Reinforcing structures such as pillars, reinforced concrete beam stiffness couplings Lenton improves the ratio between the reinforcement and concrete by eliminating half of the bars in the area of ​​overlap. This connection allows the valve to reduce the size of columns and other structures in the design and get through this maximum area of ​​the building. Figure 6 shows the options for reinforcing columns overlap and couplers Lenton. With the figure shows that the connection Lenton reduces the percentage of reinforcement structure and accordingly the cross-section of the column, while maintaining its load capacity. Due to these factors can save concrete, rebar, formwork systems costs, etc.

Fig. 6. The possibility of reducing the size of the columns in the design